1. Field of the Invention
The present invention relates generally to a wide angle lens for portable electronic devices such as mobile phones and, more particularly, to a very compact wide angle lens having an angle of view up to about 70 degrees.
2. Description of the Related Art
With the ongoing development of microcircuitry and multimedia technology, digital cameras are now in widespread use. High-end portable electronic devices such as mobile phones and PDAs (Personal Digital Assistants) are being developed to be increasingly multi-functional. Many of these portable electronic devices are now equipped with a digital camera. Conventionally, an angle of view of a lens for digital cameras incorporated in portable electronic devices is between 50 degrees and 60 degrees. Such digital cameras have a small imaging area, so it can not satisfy some special purposes such as imaging a large area when users snap self-portraits. When a user use such a digital camera to snap self-portraits, the captured image area is limited to his/her face by a short image distance and the narrow angle lens of the digital camera.
A wide angle lens has already been disclosed which achieves an angle of view of 70 degrees or more, including, successively from an object side, a first lens L.sub.1 composed of a double convex positive lens, a second lens L.sub.2 composed of a double concave negative lens, and a third lens L.sub.3 composed of a meniscus positive lens with a convex surface thereof directed toward an image side. In this case, though the angle of view of the lens exceeds 70 degrees, the full length of the lens is longer than 21.8 mm. Therefore, at such a length, the lens is too large to be equipped in the portable electronic devices. In addition, as the maximum aperture of the lens is f/8, the camera equipped with the lens needs an additional flash to provide enough light, which would yet further augment the size of the portable electronic device.
Accordingly, what is needed is a very compact wide angle lens having an angle of view up to about 70 degrees.